Texture Paint not working right?
Texture paint means to hand paint with color, brushes etc over a texture applied to a UV mapped surface. 

So, you must have a UV map, and then assign the texture to the UV map. This gives you a lot of choice to wht part of the texture is assigned to which UV face. You could also decide (or get) to have the same texture over all the UV faces (eg: a cube with a logo on all faces). If you have this or similar situation, when uyou paint in the viewport over the faces, you paint over a texture that is also mapped to other faces, so, you paint goes everywhere...

see this



or a simple cube



Try to see your UV map in the UV/image editor, and check which UV face is mapped to which texture part, berfore painting. Practice with a simple cuve first, and try what happens by


just creating a new uvmap in the object data panel on the right, "plus" button
instead, pressing u over the object in edit mode, all faces selected, and choosing different options


eg: selecting smart UV projection



you get something that behaves probably more as you intend...